text:
Do ultralights need to have EPA-compliant engines in the USA and Canada?
Do ultralights need to have EPA-compliant engines in:

The USA?
Canada?

Just wondering if you could use a hobby type 2 stroke engine for a twin engine Lazair type ultralight.  I don't think they are EPA compliant.
I know some people use them.  Just wondering if it's actually legal?

No such thing as EPA compliance on General Aviation engines or ultralight engines for that matter.  You buy a piston engine from Continental or Lycoming, it has no pollution controls of any kind. It's like it's 1960.  There just aren't enough of them to make any real impact, so they get a pass.
Pretty much anything goes for a Part 103 Ultralight in the US or what is called a "Basic Ultralight" in Canada.  Whatever suits you.

"Aren't enough of them to make any real impact" is arguable when general aviation engines spew lead out of their exhausts.

The lead pollution is inconsequential in the general scheme of things.  Microscopic compared to leaded fuel in cars.  If you grounded the GA fleet it would make no difference to anything that you could measure.  Me, I use auto fuel in my plane. The low octane engine is WAY happier on that.

I disagree sir, I think that lead from GA plane exhaust may make a big difference to families with children living near busy GA airports.

It's like fretting over a guy smoking a cigarette across the street.  In any case the rules we are talking about with respect to engines themselves have nothing to do with leaded fuel.


text:
Can you operate regular commercial flights from an airport that is uncharted and not in the national AIP?
Is it possible to operate regular, commercial flights from an airport (aerodrome) that is not in the national AIP, and for which there are no charts, maps, terrain information, obstacle information, NOTAMs etc.?
Here in Mongolia there are 23 airports listed in the AIP (ETOD is already collected and published for free) but there is discussion about removing all of them except Chinggis Khaan International Airport (ZMUB). That means, there would be no information available about those airports. Would they still be usable for flight operations?
(Related to this question.)

I don't completely understand your question. Are you asking if it's possible to operate regular flights from uncharted airports? The short answer is probably yes for private flights in light aircraft and no for larger aircraft and commercial flights: apart from practical navigation and flying issues, regulations and insurance companies might not allow it. But I may be wrong, if you can give us more information or examples about the flights and airports then someone may have a good answer.

@Pondlife Yes, You have understood correctly as uncharted airports, Currently there are 23 official Aerodromes(domestic), and they have appropriate aeronautical charts according to Annex-4 ICAO, But what happens if omit/remove/delete them from AIP of Mongolia.

@Pondlife Reason is one member of audit team at my work is saying like: "From 12 November 2015, AT AERODROMES REGULARLY USED BY INTERNATIONAL CIVIL AVIATION, electronic obstacle data shall be provided for all obstacles within Area 2 that are assessed as being a hazard to air navigation.” is meaning only Chinggis Khaan Airport but in the Annexes and Documents of ICAO, "AT AERODROMES REGULARLY USED BY INTERNATIONAL CIVIL AVIATION," phrase is frequently used for Aerodrome chart-ICAO, Instrument Approach Chart-ICAO ..... etc, this phrase is everywhere but not many people knows its meaning.

I've edited your question to include more information from your comments. If I got it wrong please reverse or edit again.

Short answer is yes, accordingto ICAO regulations.It depends though on  factors such as local aviation legislation. A PA34 departing from an uncharted private aerodrome weekly to deliver mail is a regular commercial flight. Nothing wrong there according to ICAO. Factors such as NOTAM terrain etc as you mention, ought to be dealt with under Rules of the Air Annex 2  as separate from other regulations such as on aerodromes Annex 6

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text:
Will prior hospitalization for alcohol intoxication prevent the issuance of a first class medical cert.?
I recently went to the hospital for alcohol intoxication, will that cause any issues getting my first class medical exam this week? I live in the US, I am a college student and I have rarely drank before; this was mostly a case of not eating and not drinking often. And trust me I don't even want to touch a bottle of alcohol for a very long time.

This is more a comment than an answer to your question, but, if you're in the U.S., AOPA offers advisory services to members regarding how various factors may effect getting a medical and the best strategies to pursue. Contacting them before trying to get a medical would be a good idea if you have any sort of issue that may raise red flags for an FAA medical (of which this most definitely is one.)

Search for HIMS and alcohol on PilotsOfAmerica.com They have a couple of specialist AMEs who frequent the site. Pay one of them for a consult. You will almost certainly need to spend 10s of thousands of dollars and several years to convince the FAA that you should be issued any medical, let alone a First Class. And you can never touch a drop of alcohol again. It’s doable but difficult.

Possibly, but not necessarily.
First, nobody here is an AME, and a message board is the wrong format, if any of us were, to ascertain all the relevant facts.
Second, you'll need to put that hospitalization on the form you fill out for the exam. To omit it would be a criminal offense, so don't do that.
There are at least two things the AME will consider about what happened. First, is there any lasting damage from that incident? Second, does this indicate enough of an issue with alcohol that it has to go to OKC for their consideration? Both of those questions turn on the specific facts of your case. If both are "no" then your chance of losing the medical may be pretty low. Otherwise... it's all about how your case stacks up with the FAA rules and procedures.
Your best answer may be to consult with one AME to whom you are NOT applying for the medical, and get his expert opinion. Then, with that knowledge, apply (or don't) to your AME for the Class 1.
But please don't substitute internet forum opinions for professional medical advice from an actual doctor.

In addition to seeing an AME without the application for the medical in place, seeing an addiction counselor to obtain documentation affirming there isn't a pattern of abuse would be helpful in case the AME may have concerns.  They don't want to be the sole decider without a separate expert opinion I would assume.

IMO for the sake of this site be as helpful as possible, this question should be answered in such a manner the answer(s) covered more than one jurisdiction. So answers for  FAA, EASA etc.

@Jpe61 Answering medical questions completely and correctly for even one country is a challenge. I agree FAA and EASA answers would be most useful to future readers, but SE’s layout would need a specific question for each.

I have to agree with you more than with me

Ok, but the consultation with an AME would enable the prospective applicant to know ahead of time more precisely what that would look like in this case and what sort of timeframe & ballpark cost to expect in this case. The salient point remains, go talk to an AME about the specifics of your case, rather than relying on one-size-fits-all/most/somebody advice from an internet message board as the last word.

First of all, do not go through with an “exam” at this point. Change it to an “eval” appointment with the AME. The fee will likely be the same, but if you get bad news, it won’t go on your record.
Second, ask your AME if he would issue a medical for an applicant with your recent history (and any other unrelated medical conditions or history you might have). If so, then you can make another appointment for an actual “exam” without the uncertainty you face right now. Unfortunately, this is quite unlikely.
Your AME will probably tell you that your application would be deferred. This means he could not issue you a medical and would be required to forward your application to OKC for a decision, where it will eventually be denied and you will be told to reapply through the HIMS program. And you will have a long, difficult and expensive road to travel, but the sooner you get started, the sooner you will be flying.

In all honesty a few words of advice:
You really have to ask yourself a couple of questions:

how did I get so wasted?
why did I get so wasted?
what is the pattern of my drinking?

Tendency to consume alcohol habitually mixed with aviation is like alcohol & ammo. Risky at best.
AME will ask questions about your incident for sure. Don't put your life and the lives of the others at risk and lie or tell alternate facts about your drinking. If you have a problem, it'll come out sooner or later. If you don't, best of luck with your medical.

Just to be clear, I'm not suggesting OP has a drinking problem, we all make one-off mistakes in life. However, if he has, it really does not matter where he lives and thus under which aviatory jurisdiction he falls under. Alcoholims and aviation do not mix, even if one with such tendencies might be able to get a medical. The real problem is, ask 10 alcoholics if they have a drinking problem, 8 will say no. The heaviest drinkers may be caught with appropriate blood test, but this is not 100% sure. Aviation is such a high status activity it attracts all kinds of weirdoes. Believe me, I know...

... and again, I do not suggest OP falls into this category, just saying ppl who should not fly sometimes go to great lengths to get a licence. More often than not, it ends badly.

I am well aware my answer misses the target set by the question. However, I do have a habit of stretching the boundaries of ASE where I see clear justification for such action. Correct, question was not about whether there is a drinking problem or not, and we of course are not able to answer that here. OP must consider that oneself. Fact of the matter is, there was at least a single occasion of drinking problem, one does not get hospitalized for alcohol intoxication if a consumption related problem did't exist. Regulators have good grounds for their strict attitude towards substance abuse.

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text:
Why was the Vulcan bomber used for the Falklands raid?
There is a lot of information about this complex operation. But can anybody explain why they chose to use an aircraft? They could easily shoot cruise missiles from a ship or ballistic missiles from a nuclear submarine. The easiest and quickest option would be just to shoot an ICBM directly from the UK using a conventional warhead. Just put the coordinates in and task done. No risk to anyone! I think the UK had all the needed technology by that time.

Can you provide a reference for either cruise missiles or ICBMs that the UK would have had in 1982?

I think they had UGM-27 Polaris and they were cooperating with the USA. https://en.wikipedia.org/wiki/Polaris_(UK_nuclear_programme)

Related: https://history.stackexchange.com/q/14254/1773

IMHO this question belongs to history.sx.

@ReinstateMonica-M.Schröder there does not seem to be a consensus on considering this question as off-topic here, so there is not a case for migration.

Because all of Britain's adversaries were either nearby (Warsaw Pact) or too far to economically fight (China).  Since Britain's weapons only needed to reach the Caucasus, they simply never developed ultra-long-range assets like the Tu-95 Bear or B-52 Stratofortress.  Unfortunately no-one was willing to provide any of those under Lend-Lease.
Honestly, even if the British had appropriate cruise missiles (they did not), they would have no reason to own ones with the range to hit the Falklands from Ascension.  Nor would they have any reason to need ICBMs with the range to hit Falklands from the UK (they wouldn't have ICBMs in Ascension, who would they nuke? The Congo? Guyana?)  Again the enemy is in Europe, so everything is sized and positioned to go just that far.
Your question takes for granted the pre-existence of weapons systems like the "down a chimney" Tomahawk.  Honestly, the British inability to do anything but have their SSN crews shake their fists at the islands, was a major impetus in developing those new families of weapons. Every major force watched with keen interest and thought "Gosh, what if we had to deal with one of these?"
However, they certainly did have relevant weapons: Aircraft carriers.  This type of mission is the reason carriers exist.  They could project power from the Spratleys to, indeed, the Falklands.
Further, there'd be little point to using cruise missiles or ICBMs before the main force was in position to make good on the advantage.  And once the main force was in place, they could strike from there, and did not need long-range weapons.

Obviously, Britain did project their main force with a carrier group but at the same time did conduct the Vulcan strikes (operation Black Buck we are talking about) in advance of the main force. So this somewhat contradicts your last paragraph, doesn't it? At least i don't get the point as the same argument could be used for not needing the Vulcan strikes.

@MichaelMacAskill That's what i'm saying! There were good tactical reasons to launch a long-range raid against the airfield before the main force arrived. But this means that employing long range cruise missiles would have made sense just as well, if they had been available. Harper seems to doubt that in his last paragraph.

Britain did not operate cruise missiles in 1982, the closest thing they had was antiship missiles with a range of ~100 km. Blue Steel was out of service by then, and was designed for a nuclear warhead.

@Hobbes I thought we settled that in earlier discussion.  I didn't say they did, I was saying, if they even had such, it would have been irrelevant since they never would have had a reason to field a cruise missile with such range.  Edited.

@Scrontch I won't deny the accusation, yes, this is me doubting the usefulness of the Vulcan strikes.  It was too hard to hit the field precisely without risking the bomber. And really, the whole enterprise risked the bomber, as it (too m)any of the tanker chain failed, they could lose not only the bomber and crew, but tanker(s) as well.

@Harper they had sufficient tankers on standby for the return journey such that they could abort at any point and not lose a single aircraft due to fuel exhaustion - South America was also always in minimum fuel range of the chain, with designated alternative airfields there (see Black Buck Six) should refuelling be impossible

The Vulcan crews were also not unfamiliar with the concept of no-return raids. Remember, the purpose of the V Bombers was to drop nuclear weapons on the USSR. Not that no-return raids were an option here, obviously.

And of course they couldn't use ICBMs they didn't have... And their SLBMs were all nuclear tipped and firing one from anywhere would instantly have caused a Soviet counterstrike to the UK as they were assumed to all be pointed at the USSR.

By "shaking the fists", you mean that British SSN crews were somewhat reluctant to new weaponry?

@totalMongot I mean the British SSN crews did not possess any types of weapon usable in that fight. Subs of that day had a) torpedoes, which requires the enemy step into a boat.... and b) pistols and maybe rifles, which requires sending sailors ashore, or operating on the surface very close to land (bad, bad idea if they have artillery).

Ok I see, thanks for the answer

This is borderline as an aviation question but I will answer it anyway.
They didn't use those weapons because they did not have them at the time:
Conventional cruise missiles did exist but most were nuclear, and the UK didn't possess any conventional ones.
ICBMs with conventional warheads did not and probably still do not exist because they are not a good idea:

Their capacity is low: A sub launched ICBM has somewhere around 2.5 to 3 metric tons' throw weight, much of that would be taken up by warhead guidance, thermal protection and other necessities so your actual warhead would be maybe 1000kg, or 2200lb. That's not that big a conventional bomb, and it could only launch one. A fighter bomber could drop 2 of those. The Vulcan bombers on the raid carried 21 1000 pound bombs.
They aren't accurate enough: a nuclear weapon can be a bit off and still destroy its target utterly, a conventional weapon needs a great deal of precision. The Polaris missile had an accuracy of 3000ft (900m). That's okay for a nuke, it' still ruin someone's day, but completely inadequate for a 2000lb bomb. More modern ICMBs have more like a 100 meter accuracy, which is a lot closer but still not good enough for a conventional bomb
They are expensive: that's a lot of cash for a 2000lb bomb that probably will miss
Launching one could start WW3: If you launch an ICBM someone is going to see it and if they think it might be directed at them a retaliatory strike could be the answer. The world has come perilously close to this more than once, it simply isn't worth the risk!

I have to agree to some degree. But Germans during WW2 used V2 with conventional explosives and of course those rockets were very expensive. I think they also used V2 trying to take down a bridge in France. Now I think that 40 years later UK actually didn't have any technology that was ready available for this task.

Vulcan was lucky to avoid air defence that time. Ballistic missiles had zero counter measures.

The V2 was very inaccurate @Andrius, best accuracy they got was to within 2km of target, average was around 12km. That's good enough to hit a city and cause damage, not a precision weapon by any means.

@Andrius: Also the V2 was travelling a much shorter distance, and was intended as a terror weapon rather than accurately aimed at a target.  Not very useful when you're trying to target a smallish number of troops & equipment on an island where sheep outnumber humans by more than 100:1.

It's important to explicitly note that the point of the Black Buck raids (other than to give the RAF something to do) was to disable the Port Stanley airstrip.  Black Buck Two missed its target by about 400–500 m, which meant that it didn't hit the runway at all.  An ICBM with a 900-m accuracy would probably do even worse.

I feel there's one other factor - resolve / morale.  Launching an ICBM demonstrates very little resolve;  it's kinda just pushing a button and spending a ton.
Launching an aircraft raid with so many bombers and refuellers on an area considered out of range shows that not only that every resource will be thrown at them, but that everywhere they thought was safe, isn't.  The best sort of fighting is the one where the enemy surrenders - and showing that there was no safe place to hide is always a factor to this,

Launching one could start WW3 - Yeah, exactly.  Imagine the UK explaining themselves for the 30 minutes that thing was in the air.  "No, really, guys, it's just a little iron bomb - no nukesey-s, promise!"

The Argentinians complained to high hell when it was revealed that the British task force set sail for the Falklands with nuclear weapons onboard.  Those weapons were offloaded onto vessels returning to the UK during the voyage and were never intended to be used during the conflict, but it created quite the political storm years later when it all came out.

There was a project to conventionally arm Trident at one point. (Actually you don't need any payload at all, as the KE gained during re-entry is enough to wipe out a few city blocks on impact). The problem, and the reason it was abandoned, was the accidental WWIII one. If there's ICBMs flying and some nation's survival relies on launching a second strike before the first one hits, do you trust your country's survival cool heads and radar?

@Andrius the V2/A4 was hardly an ICBM. It'd be classed a short range ballistic rocket today, not even an IRBM, with its range of a few hundred kilometers. Think Lance or Scud type weapons. The UK had those but no handy island within a few hundred kilometers of Argentina to stage them...

The UK needed a surgical strike to neutralize the Port Stanley airport in the Falklands so that Argentine airplanes based there couldn't attack the coming UK convoy or the impending UK ground attack.
An attack by carrier airplanes wouldn't work because the carriers, and the accompanying task force,  would also be in range of the Argentine planes based in Port Stanley.
Using nukes against the airport at Port Stanley would have destroyed Port Stanley and all the UK citizens there.

This hasn't been explicitly said, so: The UK didn't have cruise missiles or ICBMs with conventional warheads at the time.
The Trident II D5, the UK's only ever ICBM, entered service in 1994: BBC.
As for cruise missiles, the BGM-109 Tomahawk has been introduced in 1983 (US) and 1998 (UK): Royal Navy.

The UK had Polaris as well, before Trident. Same story though, no conventional capability.

Someone mentioned the harrier wasn't able to carry a bomb heavy enough to crater the runway. The Vulcan's dropped 21x1000lb bombs on the Falklands. The Harriers in the Falklands dropped 1000lb paveways (Laser guided). They could carry 2 normally perhaps even up to 4. So they could and did drop the same size of bomb, probably more accurately. Though there was radar controlled guns and SAM that would have been made it very hazadous for low flying aircraft. Though the harriers did raid the airport on occasion.
Some of have suggested there was inter service political rivalry. The Vulcan raid was a another means for the RAF to contribute to the war. Though the Harrier GR3 pilots were RAF.
It was probably a combination of a lot of these factors.

The Harrier were not within range until sometime later, as the aircraft carrier needed to sail from the UK.

As Ian suggests, by the time of the initial Black Buck operations, the fleet was not within range of the Falklands which would have allowed them to carry more than a single 500lb bomb plus fuel, and the runway needed to be closed so that the Argentinians couldn't base fast jets there to use against the fleet.  It wasn't until later that the GR3s came within range that allowed them to use the larger bombs, but the fleet would have been well within loiter range of Argentinian fast jets from Stanley at that point, which meant extreme risk.

Note that Black Buck switched to anti-radar missions from BB4 (with one final bombing mission later on, mainly for weight of attack against fixed Argentinian positions - something that would have required a mass GR3 attack and they were already overworked).

The runway was never closed. It operated throughout the war.

My comment was to point out that Harriers can also carry 1000lb bombs. The raids didn't shut down the main radars. They damaged secondary radars which were repaired. They didn't close the runway, it operated throughout the war. Its dubious if the fasts just could operate from Stanley, even if was undamaged. The Black Buck Raids were fantastic airmanship though.

@SeaCatS it was closed to fast jets for the majority of the war (initially because of the damage, and later on because of the threat of attack), and remained open for use by Pucaras and Hercs.  The raids did their jobs.  Whether operating fast jets from the airfield was dubious or not, the British government and military didn't want to take chances there.

As noted in a comment, the UK did have access to the UGM-27 Polaris submarine launched nuclear missile.
Launching a missile from a sub ranged a few hundred miles (or even a few thousand miles) off-shore would have been significantly less risky to UK military personnel and equipment. However...
Launching nuclear warheads against a target that you intend to occupy, as opposed to completely annihilate and make uninhabitable for a century or two (or three), is somewhat counter-productive. It also tends to, um, raise eyebrows in the international community.
Since Hiroshima and Nagasaki, no nuclear weapons have been used against actual foreign targets or people. Doing so would have been absolute political suicide for Thatcher and company, and would have most likely brought extreme backlash and sanctions against the UK as a whole.
Oh, and don't forget the numerous UK citizens who were actually living in the Falklands would have just been killed by their own government.

The question isn't asking about nuclear weapons use @FreeMan, but conventional warheads.

In point of fact, nuclear weapons would not have made the target uninhabitable for anywhere near a century.  Both Hiroshima and Nagasaki are thriving cities today.

As others have noted, ICMBs were designed for delivering nuclear warheads, not conventional. Delivering conventional warheads would be inefficient and reasonably ineffective. Using the ICBM, as queried by the OP, would have most likely delivered a nuclear warhead with the impacts I've noted. Also, sure, the Falklands may not have been uninhabitable, @jamesqf, but a little hyperbole helps drive the point home that this would have been a bad idea.

@GdD OP asked about ICBMs which are pretty much all nuclear (as noted in your answer). This answer explains why a nuclear and therefore ICBM options wasn't viable.

@Notts90 The question asked about "shoot[ing] an ICBM directly from the UK using a conventional warhead." so this is an answer to a question that was not asked and to which the questioner probably already knows the answer.

@sdenham I still disagree.

Because they could (just barely)
There is universal consensus that Black Buck served no military purpose. It did not impede Argentinian military efforts in any significant way.
Its purpose was not to be useful though. It was primarily to make troops there feel that the UK was supporting them. It was a morale-boosting exercise, nothing more (or less).
It did also have a second purpose too, which was to serve notice on the Argentinians that mainland Argentina was vulnerable to nuclear attack by Vulcan bomber.
Which renders the question moot. Whether or not the UK had any alternative abilities, it wouldn't have mattered because bombing Argentinian positions effectively was never the real goal.


text:
What is the reason for allowing pilots to take Pilot Aptitude Battery Test (PABT) only once?
Indian Airforce conducts a test called PABT (Pilot Aptitude Battery Test), for anyone who wishes to be a pilot. This test can be taken only once, and once you fail it, you can never appear again (which inherently disqualifies you from being a pilot in the Indian Armed Forces). Why is such a test so important, and how does failing in it reflect on your piloting skills?

If you disqualify once, they dont allow you to take it again. So that means, no matter of practice is going to make you better (acc. to this logic). Thats why I asked

Is this scientific? or its your opinion?

I too think like that,  but I posted the question to get some exact answer

The question title as it stands does connect the text- consider rephrasing it such that it summarizes the text, e.g. add "What is the reasoning for Pilot Aptitude Battery Test (PABT) only allowing one test?" (also helps other people to find it later)

A few thoughts:

They have no need in getting repeat candidates if the selection pool is  sufficient (which I imagine it is). Starting to accept repeat candidates would also make it harder for first timers, resulting in more work and tests for everybody. People also won't go for the fun of it, but will make their single attempt their best attempt.
I believe they would rather want you to nail it on the first attempt as part of the test. In other words: how do you respond to a new situation, how to you respond to the stress of knowing you have one attempt, etc... It would be effective for their purpose on multiple levels. This is more effective than you returning a second time and learning how to do the test.

While I can't comment on other air forces around the world, I know that German Lufthansa implements the same policy for acceptance.

The one time only policy makes it somewhat of a "life or death" scenario, which is good to help identify how someone copes with that type of stress. Excellent point!

The goal of this kind of testing is mainly to identify those candidates who are most likely to succeed in pilot training and who can do so with minimal delays. Armed services (and airlines who offer cadet training) around the world sink tremendous amount of resources into training their pilots and are taking a significant financial and opportunity cost risk on each candidate, so proper selection critical.
Designing tests meant to capture aptitude is no small task, and validation of the measurement instrument is an integral part of it, so it's probably safe to say that there is (or was at the time of design) at least some fairly significant support for correlation between performance on the battery and future performance as a pilot.
For what it's worth, keep in mind that there are almost always more candidates than actual pilot slots. Failing to be selected for a slot doesn't necessarily mean that you aren't a good pilot or that you couldn't do the job, but rather that, at that particular moment in time, in the evaluator's opinion, there were other candidates who were better than you. To illustrate using a metaphor, all drivers competing in Formula 1 are excellent race car drivers, but only one of them can win the race.

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text:
What are the requirements for foreigners to join the RAAF as a fighter pilot?
What are the requirements for a foreigner — I'm from Cyprus — to join the Royal Australian Air Force (RAAF) to become a fighter pilot?

thats hardly all the requirements is it? and ive looked there already

Did you tried contacting them ?
https://www.defencejobs.gov.au/airforce/contact/default.aspx?service=3

That's simply the recruiter contact form. I'm sure they'll have a long list of questions & requirements to follow up with. I think @Antzi's point was that you'll need to contact them to get all the requirements.

Are you asking about the special requirements for foreigners, or just all the requirements?

Only citizens of a country can apply in the government jobs (including armed forces) of that country. There can be some exceptions but I hardly doubt that a foreigner can be hired or trained for any position in military which has access to classified information. Being a fighter pilot even has more restrictions.
Royal Australian Air Force does not hire any foreigner:

Can I apply if I am not an Australia Citizen?
To be eligible to join the Air Force, you must be an Australian
  Citizen.

According to Recruitment Centre of Australian Defence Force, this page lists the proofs required for citizenship.

It is not unusual for permanent residents to be able to be hired for at least some jobs. For instance, you can enlist in the US military as a permanent resident; you must become a citizen to become an officer, and some branches make you become a citizen to reenlist, but you can become a citizen much more easily once joining the military. Australia seems more restrictive of permanent residents, but they can still be hired under some circumstances. They may not qualify to be a pilot, but they can be hired by the RAAD.

Also, foreigners can certainly qualify to join if they first become naturalized citizens. They're not really "foreigners" after becoming naturalized, but there is a path from foreigner to air force pilot.

@cpast The article I referenced does talk about permanent residents. And naturalized citizens are not foreigners, they are citizens.

It might be true for the RAAF but it isn't in general true around the world. Foreign residents used to be impressed into the US Army by the draft during the Vietnam war (and some are still required to join the Selective Service List) and certainly many commonwealth citizens join the British forces today by choice. OP can join the (British) RAF if she/he wishes.

Further, there is a large difference between joining the RAAF and being an RAAF fighter pilot. Numbers from the USAF, but I expect the RAAF isn't much different: Currently 326,855 active duty. 12,568 pilots (of all aircraft types). I'd guesstimate that no more than 1/3 of those pilots fly fighter jets. So maybe 1% of all active duty personnel fly fighters.  USAF Demographics, 2021 - https://www.afpc.af.mil/About/Air-Force-Demographics/


text:
How do fast-flying aircraft avoid overheating?
As a follow-up question to What is the typical temperature of an airliner's hull during flight? I wonder how very fast airplanes, such as the SR-71 mentioned, avoid overheating with a total air temperature outside of more than 400 degrees Celsius.

The 400 degrees mentioned is only present in the stagnation point (the only place where the speed is zero), as soon as you move away from this (imaginary) point, the temperature drop will be considerate.

To avoid overheating, the usual trick is to select the right material:

The Concorde used a special aluminium alloy, called Hiduminium, which had higher strength at elevated temperatures and allowed the Concorde to cruise at Mach 2.02. Aluminium melts at 660°C.
The MiG-25 used stainless steel instead of aluminium to make its top speed of Mach 3.1 possible (top speed without engine damage was Mach 2.83). Titanium would had been even better, but was expensive and difficult to work with at that time. Stainless steel melts between 1400°C and 1450°C.
The XB-70 used titanium in addition to stainless steel. Its cruise speed was also Mach 3.0. Titanium melts at 1668°C.
The SR-71 used titanium for 85% of its structure to allow a cruising speed of Mach 3.2.
The X-15 was built from Inconel-X, a nickel-chromium alloy which has excellent strength at high temperature (it starts to melt at 1393°C) and allowed it to go up to Mach 6.5.
The Space Shuttle used a ceramic insulation on top of the load-carrying aluminium structure which kept the heat away from the structure during descent. Note that the Shuttle had to be connected to a heat sink to cool the on-board systems after landing.

The next trick is to fly higher up where air is less dense. Lower density does not reduce the air temperature, but it reduces the heat flow so the airframe will settle at a lower temperature. Remember that the eventual heat is the combination of convection, radiation and heat conductivity. Flying high up allows especially the top surface to radiate heat freely into the black of space above.
The hottest aircraft ever was the North American X-15 A-2. For a speed record attempt, the whole aircraft was covered with pink, ablative paint so the process of sublimation would carry some more heat away. To protect the paint from liquid oxygen, a white topcoat was applied also.

X-15 A-2 shortly after being dropped from the B-52 carrier (picture source). Note the small barrel under the lower fin: This was a ramjet which was test-flown on this occasion.

Damage to the ventral stabilizer. The ramjet separated prematurely due to frictional heating (picture source)
A third trick is to fly fast only for a short time. A heat-seeking air to air missile will easily reach Mach 3, but only for less than a minute. To keep the sensor cooled, a pressurized gas (argon or nitrogen) would be expanded (the AIM-9X even uses a stirling cryo-cooler). By heating the structure or using an internal heat sink, the limited heat load can be tolerated, albeit only for a very limited time.

The shuttle heat sink that you are talking about was not for mitigating aeroheating of the structure.  It was for cooling internal mechanical and avionics components.  There was no active cooling of the shuttle's heat shield after landing.

@Tristan: No, the heat shield did not need cooling, but the internals did due to the heat creeping through the ceramic foam and heating the airframe from the outside.

The SR-71 also had body panels designed to expand from the heat so they were very loose on the ground. This means it leaked large amounts of fuel at take-off. I recall reading somewhere that it would take off with a full load of fuel, go supersonic to heat the skin to close up the gaps, then need refueling because it used up almost all the fuel between leaks and expanding the skin. Then it would go about its mission.

@PeterKämpf The heat rejection for the internals was first and foremost due to their self-generated heat -- they are actively cooled from first powerup well before liftoff to powerdown well after landing.  The shuttle's tiles were such poor heat conductors that postlanding structural heating wasn't a major concern.

@Tristan Internal, self-generated heating required the Shuttle to open the cargo bay doors soon after reaching orbit, and if the doors would't open the mission had to be aborted. After landing, the doors stayed shut. So you say the external cooling just did what the radiators on the inside of the cargo bay doors did? What I learned is that the Shuttle descent was highly instationary, absorbing much more heat than it could handle continuously, and without removing the heat stored in the tiles, the structure would be permanently damaged.

@PeterKämpf There were three different cooling systems available, depending on the flight regime.  The on-orbit one was the payload bay door radiators, which created a closed system that could be used for long periods of time.  When the payload bay doors were closed, cooling switched to the flash evaporator system, which used water to provide sufficient cooling in a low-pressure environment.  Below a certain altitude, they had to switch to an ammonia boiler system.  Both the flash-evap and boiler were open systems with short lifetimes, but all three were used to cool the same components.

I think there was a post-landing close call on one of the shuttle flights because of improper shutdown of the cooling systems.  Having trouble finding a source right now--think I saw it on a Lessons Learned video a while back.

I'd like to answer with a focus on the SR-71, since I happen to have a book that gives details on its design.
Ben Rich was the lead of the propulsion and thermodynamics group for the SR-71, and Kelly Johnson's successor as head of the Skunkworks for later programs.  In the "Faster Than a Speeding Bullet" chapter of his memoir Skunkworks (pg 203 in the first paperback edition, 1994), he writes:

...
  I volunteered some unsolicited advice about how we could use a softer titanium that began to lose its strength at 550 degrees.  My idea was to paint the airplane black.  From my college days I remembered that a good heat absorber was also a good heat emitter and would actually radiate away more heat than it would absorb through friction.  I calculated that black paint would lower the wing temperatures 35 degrees by radiation.  But Kelly [Johnson, head of Skunkworks and the then-A12 project] snorted impatiently and shook his head...
  Overnight, however, he apparently had second thoughts..."On the black paint," he said, "you were right about the advantages and I was wrong."  He handed me a quarter.  It was a rare win.  So Kelly approved my idea of painting the airplane black, and by the time our first prototype rolled out the airplane became known as the Blackbird.

The chapter goes on into greater detail on various unique material selections:

stainless steel hydraulic lines
Hastelloy X ejector flaps
Elgiloy control cables
Gold-plated plumbing lines
Titanium screws and rivets
Special rubber for the landing gear wheels, which were then inflated with nitrogen
Jet fuel with a higher flash point (JP-7)

Pg 205:

The fuel acted as an internal coolant.  All the heat built up inside the aircraft was transferred to the fuel by heat exchangers.  We designed a smart valve -- a special valve that could sense temperature changes -- to supply only the hottest fuel to the engines and keep the cooler fuel to cool the retracted landing gear and avionics.

Pg 207:

We designed the cockpit air-conditioning to bleed air off the engine compressor and dump it through a fuel air cooler, then through an expansion turbine, into the cabin at a frigid minus 40 degrees F, which lowered the ovenlike 200-degree cockpit to a balmy Southern California beach day.

So I guess there's three generic design principles embodied here:

selection of materials to withstand high temperatures
rejection of as much heat as possible--here by radiation from the aircraft's surface and convection out the engine exhaust via the fuel
sequestration of heat away from critical areas, as much as possible

I'd add a note about using fuel, and structure, as heat sinks, as well. Before ablative techniques, atomic and nuclear warheads on missiles had copper heat sinks

I already have a note on the fuel being used as a heat sink.  If you have something about the structure being used as a heat store, feel free to add your own answer (to this older question, I just noted a typo in my answer and changed it).  I'd be surprised by the structure being used as a sink, since it seems like that's what you'd try to pull heat away from to reduce thermal stresses.

Sorry, I was too terse. The "three generic design principles" ought to be "four generic design principles" and specifically mention sinks. It is possible to infer sinking (and exporting) heat from the second item, "rejection of as much heat as possible". But stating it clearly seems simpler, and is amply supported in the text above.
Yes, in 2016 it is surprising to have structure intended as a heat sink, but heavy lumps of copper were part of early re-entry vehicle design. That's why they should be mentioned.

Hmm.  Sinking is really only part of the process, though.  You sink the heat to the fuel because you're about to dump it overboard.  Hence the hottest-fuel smart valve.  The rejection does encompass both radiation and convection...maybe I'll expand that.
I'm not going to go into the structural heavy lumps of copper thing.  I limited the scope of my answer to SR-71s because it's a question about fast-flying aircraft and I had a good SR-71 resource.  I don't know anything about using structure as a heat sink in fast-flying aircraft.

There are multiple ways to avoid overheating.

The simplest method is to use a high temperature material- like Titanium in SR-71 or steel alloy in Mig-25; in Concorde, a special aluminum alloy (AU2GN) was used. In case of other aircraft, steel or Ti is used in stagnation points (like wing leading edges), while the other exposed surfaces are made out of other materials.
In SR-71, the fuel was used as a heat sink to dissipate the heat generated in the airframe.
In X-15, an ablative insulation was used to overcome heating problems:

The airplane was covered with ablative insulation designed to permit flights to Mach 7.4. A silicone elastomeric ablator was sprayed on in variable thickness appropriate to the local heat loads. Leading edges were protected by a related erosion-resistant material applied in preformed sections

Aerothermodynamic design is important for high speed aircraft. For example, when NASA tested a dummy ramjet in X-15, the mounting pylon nearly failed due to interference heating, with leading-edge heating rates of the order of seven times compared to those without interference being estimated.

Failure of pylon due to interference heating from dummy ramjet, image from history.nasa.gov

To help reflect and radiate the high amount of heat produced during supersonic flight, the Concorde had a high-reflectivity white paint that was about twice as reflective as the white paint on other jets.


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Why don't the US Navy Blue Angels fly Super Hornets?
The US Navy demonstration team has been flying the legacy Hornet for a long time and I was wondering why don't they use the Super Hornet? The legacy Hornet is over 30 years old and showing its age. I know there have been numerous incidents during shows where control surfaces have broken off the planes.
Why aren't they using the newer airframes? Is it the cost of upgrading? Performance concerns?

In addition to aeroalias's excellent answer, the obvious follow-up is "why didn't they do so sooner", the answer being that they don't really need to; the Super Hornet's improvements are largely around combat avionics, payload and range on internal fuel, none of which are critical concerns for a demo squadron that flies totally clean aircraft from the nearest airbase to the show and back.

@KeithS that would make a good answer

The Chinese counterparts used MIG21 derivatives well into the 21st century. When you don't need a lot of range can can cut weight by carrying minimal fuel, a lot of fighters would have much better maneuverability than in a combat situation, e.g. the Iranian F14A vs F15 story, making them capable for the job for a long time.

The USN Blue Angel demonstration team is transitioning to Super Hornets. According to this press report:

“We are supporting the Navy’s plans to transition the Blue Angels to Super Hornet aircraft from classic Hornets by providing engineering for the necessary conversion modifications. ...,” Paul Guse, a spokesman for Boeing, said Thursday in an emailed statement.

The transition will take some time for carrying out the necessary modifications including...

..., installing flight auxiliary fuel pumps that can operate in sustained inverted manoeuvres and inserting an oil pump in the tail to emit blue smoke.

...among others. Also, as the aircraft performance is different (the Super Hornet is larger and heavier, for one thing), the aircrew will have to train on the new aircraft before participating in any airshows.
A lot of the weight difference may be handled by removing the combat hardware but the size and handling characteristics will require a lot of training and practice time before the super hornet can be used in the precision flying exercises used in air shows.

Comments are not for extended discussion; this conversation has been moved to chat.


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What does the crew of a long range miltary aircraft eat during a mission?
The B-52 and other big aircraft often fly long missions.
What does the crew eat or drink?
Is there a list of recommended things to eat, or of specific foodstuff to avoid?
How is it stored onboard?

Whatever they can physically carry onto the aircraft?

to service the passengers (bombs) obviously :P

Water, coffee, 7 Up, sandwiches, bacon, frozen pre-cooked meals, lunch boxes, http://b52stratofortressassociation.yuku.com/topic/68/Food-Meals-on-BUFF-Sorties#.Vd1rlPlVhXo

This question may be extended to other long military missions.

@Simon That sounds fancier than what I eat day to day... I should become a bomber pilot.

If you went on a camping trip with a packed diner what would you bring? Its basically anything you would pack for a camping trip or a school lunch box.

@Ethan i brought sushi, beef curry, roast duck and fried noodles in my last high school trip. Unfortunately the trip was held in school due to bad weather.

BACON !!!!!!!!!

It wouldn't surprise me if they carried a version of MREs called Aircrew Build to Order Meal Module (ABOMM).

The fish! (urban legend)....

The C-5 has a large kitchen.

@usernumber enough for wedding reception?

It's not just the big bombers flying long missions; you'd be surprised how many of the sorties flying over Afghanistan, Iraq, Syria, Libya etc originate from airbases in Northern Europe with refueling stops over the Mediterranean (because closer airbases aren't available or are congested with aircraft from other forces or that have shorter ranges).
The short and simple answer is, aircraft crews eat whatever they can bring with them, that won't make a huge mess in the process. A bigger plane like a B-52 has some room to get up and move, so the pilot may take 15 minutes during ingress or egress, duck out to the entryway and eat a box lunch, then come back and relieve the co-pilot so he can do the same thing. Radar, nav and weapons systems officers typically have a little room behind or between seats to step away and eat, or they'll duck into the entryway as well.
In smaller aircraft, space is more limited, but the pilot's flight suit will still have plenty of pockets to carry food and drink pouches. There are some considerations as to the exact type of food, especially in one- and two-seat jets. A crewman has to prevent "foreign object damage" to the switches and displays in his cockpit, or else his crew chief (and his CO) will be all over him about it. Good choices include pre-wrapped bar-type snacks; granola, protein, energy, some types of candy bars, whatever. Depending on what's available in the mess hall, pilots may be able to assemble simple tortilla wraps with lunch meats and cheese, which are edible with one hand and fewer crumbs than a bread sandwich. Anything that can be put in a drink pouch, like broth or tomato soup, is also a possibility. Bad choices include things like trail mix, peanuts, M&Ms etc, as well as anything too loose to reliably keep together with one hand.
The bigger concern is, what to do when it comes back out? The B-52 has a rudimentary "head", with what amounts to a camping toilet (a bucket with a plastic bag liner and a toilet seat over the top) called the "honeypot". However, if it's used, the crewman who used it is often tasked by the crew chief with cleaning it, so it's considered a last resort. Crew of smaller aircraft have no such luxury, and unlike NASA astronauts, they wouldn't be caught dead wearing a diaper. Most fighter pilots eat a "low-residue" meal for the two or three meals before a very long mission or ferry flight, to reduce the chance they'll have to BM during the flight (some take an anti-diarrheal like Immodium as a preventive measure). Urination is a little easier to deal with, for men at least; pilots carry packets with an absorbent powder (not unlike what's in diapers) called "piddle packets". The difficulty is typically in... "maneuvering". You have to get the equipment out of your flight suit, when you're strapped down to the point of suffocation in a 6-point harness, then be able to aim into the piddle pack. Finally, you have to store this bag of piss somewhere until you get back to base, and as Rhino Driver is fond of explaining, if that base is a carrier, you have to make sure it's extra-secure, or on capture it'll go zooming forward toward the firewall and explode in a shower of damp absorbent crystals. Even if your squadron-mates don't see you getting out of the plane covered in this stuff, your crew chief will be sure to tell them all about it.

Even military operations carried for long mission would carry the dried food items which can be stored for long time, light in weight and heavy rich nutrients/calories. B-52 Bomber might carry these items which are approved by Authority and it's government.


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Why are most weapons in AC-130 on the left-hand side?
Lockheed AC-130 gunship is a heavily armed ground-attack aircraft variant of the C-130 Hercules transporter. The plane is manufactured by Lockheed and converted by Boeing.

Why are most of the guns in AC-130 installed on the left-hand side (but not right)?
Picture Source

Weapons on the other side would be useless because they'd be firing at the sky

@slebetman I think the question is not only why are there weapons on one side only but also why are they on the left and not on the right.

The picture above is somewhat misleading. In that image, it is not firing weapons at all. Those are countermeasures. "Most" of the guns on an AC-130 are not on one side, all of them are.

He is talking about the guns not about countermeasures.

I rather doubt there's an extremely good reason for the weapons to be on the left instead of right. They had to pick a side, might as well be the side the pilot sees out of. As a counter-question, why should they not be on the left?

Please provide attribution for your image.

Is there anything I can add to my answer for you?

"Developed by the USAF Aeronautical Systems Division (ASD), the gunship applied a principle adopted by bush pilots in South America. This was the use of a weighted bucket suspended on a rope from an aircraft flying a very tight continuous turn to keep the bucket stationary at the tip of an imaginary cone for the collection of mail and the like from inaccessible sites." Source: Defenders: a comprehensive guide to the warplanes of the USA, Oriole, 1989.

It is not designed to strafe, it is designed to loiter over a target or, to apply suppression fire or support fire for a sustained period of time.
It often circles a target area and a counter clockwise orbit (circling to the left) makes sense since the captain sits on the left and can keep the area in view at all times.
Therefore, the weapons are mounted on the left.

Furthermore, if you've got guns on both sides, it implies that you have enemies on both sides. That doesn't happen very often, so most of the time you're carrying guns you can't use. You could fly back and forth, but then each set of guns is only in use half of the time, while the other set is useless weight. Putting all the guns on one side means that if one of them can see the target area, they all can, so you can use all the guns, all the time.

Given your answer, I understand that to efficiently pilot this aircraft, you should seat at the left. Does this mean only the captain can do so?

While piloting the aircraft in normal flight, it follows all the same rules and procedures as any similar aircraft would. When conducting a fire mission, the required pylon turn is probably easier from the left seat, but not impossible from the right.

@ManuH, while that should probably be its own question, I would assume that while the aircraft is circling an unfriendly zone, laying down heavy suppression fire, it's highly likely that the captain would be the PF. Were something to happen to the captain, I'm sure the FO could take over and continue to circle from the right-hand seat, however, they would then have to weight the value of the mission vs addressing whatever issue has caused the captain to relinquish control.

This is the correct answer. Because circling to the left makes it easier for the captain to see what's beneath.

Traditionally, the doors most used on an aircraft (including civilian ones) are on the left (captain's) side. Often weapons are mounted in door apertures so that additional holes do not have to be introduced into the fuselage. It follows that there are more, more accessible, pre-existing holes on that side of the fuselage.

The AC-130 is the evolution of modified C-47s from the Vietnam War. At the time, a small group of USAF personnel explored arming cargo aircraft with side mounted weapons in order to bring greater firepower to bear for ground support. In particular, they wanted to solve the problem of strafing, where aircraft can only bring their firepower to bear for a short period of time, and often without a great deal of time to aim.
Captain Ron Terry was in charge of the initial effort which adapted these planes to gunship use in Vietnam in 1964:

Terry arrived at Bien Hoa Air Base near Saigon on December l. After the miniguns arrived the following week, he selected two test crews of six flight members and an interpreter, and two C-47s with relatively low flight time from the 1st Air Commando Squadron. The planes were modified to accept three minigun pods along the port side (two in the last two windows and one in the cargo door); an MK 20 Mod 4 gunsight mounted in the left cockpit window; and a selective trigger placed on the pilot’s control to fire one or all the guns.

source
Since AC-130s are now specially converted from C-130s by Boeing, and they use modern targeting sensors (IR and visual cameras), and that windows/doors are no longer large enough for the custom mounts they use to install the weapons, there's probably no specific reason for keeping them on the left except that it's the status quo.

So according to this, the guns were on the left originally because that's where the cargo door was, making it easier to install the guns?

I think it leans that way, I wasn't able to find any definitive source for the technical decisions they made.

They're on the left because the pilot has to see the aim point.  The 'solution' to the strafing problem is to do a turn about the target. By doing that your aim point is the target (no lead required.)  The AC-130 has a side-looking HUD for the pilot to see the target and adjust his turn rate to keep it at the center of the turn.

That's obviously the other option, but I don't think it's definitive. For instance, if you look at the same source I quote above, Capt. Terry says his aiming point is between the left prop hub and engine cowl.  My understanding of the site lines of the interior of a DC-7 is that the copilot would be able to see a similar position, so I don't think that was a deciding reason for making that choice.

All the guns are on the left side. The method of targeting is that the aircraft circles counterclockwise so that the left side is pointing downward. Thus all the guns can be brought to bear on the target (unlike an old frigate with guns on both sides) and the pilot can see the target as he circles.

Thanks for answering, however, I don't think your answer really added anything to the discussion that hadn't already been stated.


text:
Fighter YO-YO counter measure?
In a dogfight ("A" Scenario), aircraft "A" is being shot at by aircraft "B". In order to lead aircraft "A", "B" must turn inside "A" and will soon overshoot if "B" does not perform a defensive maneuver. "A" can force an overshoot and then turn into "B" for a shot.
("B" Scenario) To prevent "B" from overshooting, it is common practice for it to perform a YO-YO (quick climb then dive) which absorbs energy and increases the flight path which will help keep it behind "A".
In the second scenario, what options does the lead aircraft have to gain the advantage over an enemy behind it that likly is about to perform a YO-YO?

my artwork

Sort of amusing F-16s were used here, instead of older vintage aircraft.  One must realize those little turns would involve high Gs that may incapacitate the pilots.  Also, any "yo-yo" would bleed off a lot of energy and make B an easy target for wingman of A.
One "oldie but goodie" would be for A and its wingman (person) to weave and have B turn right into the wingman's line.  This is the value of teamwork.
However, these days, more realisticly, you need to dodge the opponents missile, which can be very tough.  Stealth and shoot now rule.  But old methods should still be studied.
In the second scenario, one on one, aircraft A would also try to "yo-yo", and they wind up in "a rolling scissors".  The aircraft with more power to weight and better turning rate prevails.  For identical aircraft, it would be pilot skill.  But for modern aircraft with missiles and partners, this type of turning engagement would be very rare.

Every generation of new aircraft have had "experts" saying dogfights are a thing of the past. Then a conflict occurs and the fighter with bullets starts coming out ahead. As the late Bob Hoover once said, "most victories are won by a surprise attack and not strategy or pilot skill, the dead pilot never even saw it coming..". I predict that for as long as there are aircraft (even if it is unmanned) there will continue to be close combat dogfights. It will be a long time before technology prevents clouds from masking aircraft position and surprise attack.

This may be one of the reasons the F35 C has a larger wing :).

Col John Boyd was a masterful genius who developed many concepts of aerial warfare, including the concept of specific excess power, to compare dog fighting capabilities, the OODA loop, and wrote the first USAF manual on fighter tactics, the Aerial Attack Study.  See page 72, procedures for countering high speed Yo-Yo, and page 84 for the low speed.
An excellent biography, by Robert Coram, covers his life.

He was dubbed "Forty Second Boyd" for his standing bet as an instructor pilot that beginning from a position of disadvantage, he could defeat any opposing pilot in air combat maneuvering in less than 40 seconds.

He’s buried in the National cemetery, Arlington, VA.

This answer could be improved by listing said procedures in it, as opposed to just providing a link to a PDF. This way the answer will remain relevant if the link rots away.

@AEhere.  Absolutely correct. If you (or anyone) would like to do that ... please feel free. I am a bit surprised no actually has done that, because I am sure they would get more votes than me.


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Why was the U-2 so different from the SR-71?
Both were designed for the same goals: taking photographs at high altitude, avoiding radar. Both were designed by the same company with a few years apart. Yet one is a "jet glider", with large wingspan, small chord, subsonic, and the other is a ultra high speed, delta wing airplane.
Why did these two planes took such different approaches to perform similar tasks? What would be the pros/cons of each? The SR-71 was developed later, so it could be seen as a better approach, yet it was retired, while the U-2 is still in use.

Because the requirements were different. When U-2 was developed, the requirement was for an aircraft which would fly high at 70,000' due to the (mistaken) belief that the Soviets would be able to detect and engage aircraft only below that altitudes.
Once the U-2 entered service however, it became obvious that they could detect U-2 (they complained about the overflights, though misidentifying the aircraft), and once an aircraft was shot down, it became obvious that U2 isn't going to be of much help.
SR-71, which came later, was the result of a requirement which expected it to not only fly higher, but more importantly, faster. Interestingly, the Soviets went the same way with the Mig-25R.
The main reason for the retirement of spy aircraft was the advent of reconnaissance satellites, which are immune to being shot down (not that it is impossible, but no one has done it except in tests). Spy aircraft are still operated only over areas where the threat from anti-aircraft systems are extremely limited or non-existent. At the time of its retirement, the USAF accepted that even the SR-71 is not invulnerable:

In congressional testimony, Air Force Chief of Staff Gen. Larry D. Welch identified the increased survivability of reconnaissance satellites, SR-71 vulnerability to the Soviet SAM-5 surface-to-air missile and the cost of maintaining the SR-71 fleet.

As for why U2 has outlived the SR-71, the main reason is the operating costs- the operating costs of SR-71 is quoted to be anywhere from \$85,000 to \$200,000 per hour, while the U-2 costs much less than that (incidentally, U-2s operating cost is less than that of its proposed replacement, the RQ-4 Global Hawk).
From the same source as above:

The Air Force decision to retire the Blackbirds in 1990 is based on several factors. ... The cost factor is the most significant to the Air Force because it limits expenditures in other areas. Reagan Administration Air Force Secretary Edward C. Aldridge Jr. estimated that the money used to operate the SR-71 fleet could operate and maintain two tactical fighter wings.

Interesting. If we're not concerned about being shot down, is it possible to design a "jet glider" style i.e. subsonic plane to fly , say, at 100,000 ft? I know the Mig 25 and the Blackbird could fly above that.

@Southbob The Airbus Perlan project aims to do just that. The NASA Helios has set an altitude record of >96,000 ft.

Didn't know that SR-71 was vulnerable. Always got the idea that it could outfly any missile.

@Firee anything is vulnerable, all depend on engagement parameters and equipment. It can outfly a missile if it has to trail it, but in a head on engagement it can't outturn that same missile for example. Similar with the F-117 shot down over Yugoslavia. The missile couldn't track it, but by triangulating between multiple radars positioned carefully the guidance vans could guide the missile directly.

@Southbob "jet glider" is exactly what the U2 is.  The reason it can't fly any higher is because of the weight of it's components.  Modern craft may be able to use lighter systems though (for radar and photography) so they may be able to get higher if one is ever built.

@aeroalias The latter half of this would make a great answer to http://aviation.stackexchange.com/questions/30516/why-was-the-production-of-the-lockheed-sr-71-blackbird-halted .  Right now most of the answers there don't have primary sources like you do.

First off, the U2 was an earlier design, and engineered around the philosophy that the primary threat to a reconnaissance aircraft were cannon armed fighters.  Kelly's thinking was that if he could design an airplane which could fly far higher than existing turbojet powered fighters, the aircraft could not be shot down and could conduct reconnaissance missions with impunity.
Then came Sputnik and the dawn of the missile age.
Lockheed had quietly begun to investigate higher and faster flying design which could nullify the threat of missiles using solid fuel boosters and sustainer motor to reach the altitudes the U2 flew at but the U2 continued to fly over the USSR and with great success.
And it all worked great until May, 1960 when a CIA pilot named Francis Gary Powers was shot down over the Soviet Union by an SA-2 surface to air missile.
At this point there was an impetus to acquire a newer faster aircraft for strategic reconnaissance.  The idea being that the plane could fly so high and so fast that a ground launched missile system would not pack the energy needed to overtake and shoot down the new aircraft.  This was the genesis of the A-12 Oxcart program, which struggled through a 7 year long development and flight test program before entering service with the CIA; a two seat advanced derivative of the A-12 went into service with the USAF as the SR-71 Blackbird.  Officially there have never been overflights of the Soviet Union by either the A-12 or the SR-71 due to the political risks but Blackbirds did officially overfly North Vietnam, China, Eastern European communist bloc countries, Lybia, Egypt and North Korea and were shot at multiple times using advanced Soviet made SAM systems - all without a single loss.

The main idea was completely different behind the 2 designs. The U-2 was designed in an era when the main threat to aircraft were anti aircraft guns and gun carrying point interceptors.
Neither could (at the time, and to a large extend still) reach the operational altitude of the U-2.
The Soviets tried many times to shoot one down, but it wasn't until Gary Powers (due to a navigational gamble he took to get out of the USSR in time to make a daylight landing at his intended destination, which had him fly near a Soviet SAM site) was shot down by the newly fielded strategic SAM capability of the USSR (designed against American bombers) that the idea was shown to have outlived its usefulness.

The SR-71 was then rushed through design and production to be completely different, flying not just very high but also very fast. AND its operational concept relied far more on side looking sensors so the aircraft could remain outside the target country or area and look in from the relative safety of friendly airspace (under the assumption, which was never broken by the USSR or China, that the USSR would not shoot at aircraft outside of its airspace.
Later the D-21 project intended to add a deep penetration drone to the back of the SR-71 which could overfly China or the USSR and later be recovered. Several of these drones were lost, causing top secret technology to fall into enemy hands, and the D-21 program was shut down.

Were there really D-21 shot down? To my knowledge, one never turned back, two ended their flight as planned but the film capsule capture failed and one crashed over China. The first one crashed in Siberia when fuel ran out. Boris Yelzin handed a part of it to Bill Clinton AFAIK.

@PeterKämpf I remember reading somewhere of the Chinese claiming the crash there was them shooting it down. No confirmation of course either way.

That makes it only one, not several. And I really doubt that the Chinese were able to hit something at 30km, screaming along at Mach 3.7. If they did, it was as a consequence of some malfunction maybe.

@PeterKämpf changed it into the more neutral "lost"


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Why was the P-51 Mustang not adopted by the U.S. Navy?
I've heard from many WWII aviation hobbyists and WWII vets that the P-51 was essentially the pinnacle of U.S. piston-engine fighter design; it was fast, maneuverable, long-range, well-armed, allowed superb pilot visibility, etc etc.
So, why did the Navy never adopt it? It seems there were flight tests of the P-51D as a carrier fighter, modified with a tailhook for wire capture landings, but the Navy never pulled the trigger (so to speak). What were the primary reasons behind this decision?

The P-15, like many other fighters/pursuit planes, started off not well liked.  It's performance wasn't very good either.  Only evolutionary improvements to the airframe and a re-engining with a more powerful engine allowed the P-51 to reach its full potential.

The P-51A, went into service with the RAF, and at the time it was faster than any British fighter below 14,000 ft.

The biggest driver behind the use of the P-51 Mustang in naval operations was the need for B-29 escorts while bombing Japan. No naval fighter at the time had the range to accompany the B-29's so the P-51D was selected to determine if it could be a suitable carrier operator.
The test project was named "Project Seahorse", and one aircraft was selected and specially modified to cope with carrier landings.

Navy Concept Image in Livery (Image Source)
The modifications included:

"Fin Fillet Extension" which enhanced low-speed operation.
Tail hook (for obvious reasons)
Catapult hook
High pressure tires
Higher pressure in the shock absorbers
Reinforced airframe

The modified P-51D started testing in September of 1944 under test pilot Robert Elder. The tests were carried out at Mustin Field in Phillidelphia on a modified runway fitted with a catapult and arresting cables. Throughout September 1944 to October 1944, 150 launches and recoveries were made on this modified runway. One big concern was that the aircraft would need to land around 90mph and the stall speed was 82mph, not much of a margin.
In late October 1944 the next stage of testing started, carrier landings/launches at sea. Lt. Elder made all the carrier landings at 85mph and was pleased with its handling characteristics, but there were issues:

Stall speed margin was extremely low, too low for safety
Rudder control at low speed and high angles of attack was inadequate
Landing attitude had to be very carefully controlled to avoid airframe damage
Go-arounds required slow throttle advancement. The extreme power of the Packard/Merlin engine meant that a high-power fast throttle advancement could put the aircraft into a roll or snap-roll. At low speeds this would prove a fatal mistake.

Only 25 launches/recoveries were made in the suitability trials and Lt. Elder did not believe that the Mustang had a place in carrier operations.
It was a moot point anyway. By early 1945 Okinawa and Iwo Jima were won by the allied forces. Each island had airfields that were taken over and provided a close base of operations for aerial attacks on Japan. In August 1945 Japan announced its surrender and it was official September 2, 1945. The P-51 wasn't required to be used from a naval platform anymore.
The project wasn't forgotten though. North American presented the NAA-133 based on the P-51H, which was a carrier operations "Mustang". It didn't go any further than the design stage though. In 1947 a P-51H was acquired to test new catapult equipment. Either way the war was over by that time and we didn't have to put any more effort into modifying the aircraft for carrier operations.
Here is my main source

Nice history lesson.

Could you go into a bit more on the (seeming) contradiction: "Lt. Elder made all the carrier landings at 85mph and was pleased with its handling characteristics" and "Lt. Elder did not believe that the Mustang had a place in carrier operations".

@Shane Lt. Elder is a test pilot. He's comfortable doing things on the edge and he probably felt comfortable getting it on the deck, but surely realized that the (above average) skills of a newly minted fighter pilot behind the controls of a 1200hp engine with wings would probably have difficulty in getting it on the deck without damage to them, the aircraft, other aircraft, and the carrier itself.

Something about that paint job is just gorgeous.

@Shane: There's no contradiction. What he "felt" when he flew the airplane pleased him - it was controllable and behaved well. However, when he realized that he was landing at 85mph he did not believe the aircraft was suitable because if he were to fly just 3mph slower the aircraft would not behave well and would most likely stall and crash. 3mph is enough for a gust of wind to cause a crash. Obviously, since he didn't die in a crash on that test he never "felt" the unpleasant behavior when flying the plane.

As a side note, they also tested a B25/PBJ (in navy parlance) at the same time.

Awesome history lesson ! and What a beautiful painting !

...so why not add flaps to the Mustang to enhance the stall speed margin?  (I'm assuming that the reason they couldn't land any faster than 90 was that trying to do so would break the arresting wires, or something like that?)

@Sean stopping distance. At higher speeds the length of the landing deck combined with the energy absorbing capabilities of the wires would not be enough to slow the aircraft to a stop before it went into the water at the end of the deck.

@jwenting On the old straight deck carriers, it was worse than going into the water. Beyond the cables was a barrier (similar in appearance to a tennis net). Beyond that, there were normally parked a/c or others being prepped for launch. Angle decks didn't appear until the mid 1950's.

@Gerry depending on the aircraft coming in, decks could be cleared to allow more space. Of course this would slow down operations, but so be it. They'd have to reposition the aircraft anyway for takeoff. At the time carrier operations were either takeoffs OR landings, not both at the same time.

Good answer: by the time the Navy could think about something else that aligning lots of Hellcat and Corsair, the reasons to adopt the Mustang had faded away

The P-51D's power-loading was more or less identical to that of the F6F-5; about 7.70 lb / hp at MTOW; the F6F was considerably heavier but had 30% more engine power with the R2800-1OW capable over 2,000 hp.  The F4U-1 had a marginally lower loading being about a half-ton lighter than the F6F.
So it wasn't a case that the P-51D would have been too much for for Navy pilots on account of 'extreme power', though with a lower frontal cross-section and laminar-flow wings its acceleration may have been higher.  The stalling speed would appear to have been the critical factor, largely as a result of the P-51D having a wing-area much smaller than either naval fighter.

Would the engine type have been another consideration? All other American carrier-based aircraft were air-cooled engines which could take some amount of damage and continue to produce power; the Mustang's Merlin was liquid cooled making it somewhat less tolerant to damage. Under similar conditions, a Mustang's engine could be disabled, forcing a ditching where a Corsair might be able to power its way back to its home carrier.

The flying Tigers used a few P51 successfully against various Japanese aircraft including Zeros so fear of a Zero crippling the P51 was not an issue and the P51 had already shown superiority before the US entered WWII. P38, P39, and P51 where used side by side as B25 escort on Attu (Alaska) against the Japanese invasion but for some reason the P38 was the favorite in that campaign (perhaps twin engine or the nose gear had an advantage in the very rainy mud).

@jwzumwalt the extreme range and twin engines made the P-38 more suitable for the long distance fighter patrols and sweeps into Japanese held territory than other types. Having to fly for hours over open water without anywhere to make an emergency landing if you have an engine problem makes you appreciate having 2 of the things.

The Navy did not want the complexity of the liquid cooled engine and the need to supply and store coolant. AND the coolant is FLAMMABLE another problem the Navy did not want. The liquid cooled engines were also more susceptible to battle damage. The radials were a lot tougher in this regard and would make it back with damage that would stop the liquid cooled engines. When overflying a trackless ocean the Merlin would have increased the number of pilots lost. So far as the range thing. There were P51s and long range P47Ns flying missions to Japan from Iwo so the B29s had cover for daylight raids.

...they were operating carriers filled to the brim with bombs and avgas and they were worried about flammable radiator fluid?  Sounds like someone needs to get their priorities straight...

@Sean not so much the flammability as the requirements for yet more consumables to be stored in already cramped ships. And more spare parts as the liquid cooled engines were more complex, requiring more and different spare parts as well.

The US Navy didn't need the P51 because they had the F4U Corsair, which had comparable performance, was better suited to ground attack work, and was designed from the start with a tougher structure suitable for carrier operation.

Not mentioned above is a key design criterion that changes everything:
A carrier can sail to the area of action. An airbase cannot.

Longer range is always a good thing, as the Zero demonstrated. But in a general sense, carrier aircraft don't want to be hyper-optimized for range in the same way that one would have to for a land-based plane. So for a land-based plane you optimize for weight and aerodynamics, and if that means you have a wicked stall, fragile landing gear and 1/2 mile takeoff run, well, so be it.
And so you get the P-51. By any measure it was relatively light, especially compared to its Navy counterparts. And some models, like the H, were lightened even more. These were not going to last long on carrier ops!
The P-51's wing was selected specifically for low drag, even though it was known the design gave it high landing speeds and wicked stalls. Who cares? Just extend the runway a little and all will be fine. Again, not an option for carriers.
And finally, since you have lots of airbases, you don't really need to design your planes for multiple missions. So the idea of putting an easily-hit radiator full of boiling-hot caustic fluid on the bottom where it's easy to hit and directly under the pilot? Well, don't fly low. Again, the Navy doesn't have the luxury of space, you planes need to be able to survive all sorts of missions.
And this is why pretty much every attempt to make a carrier plane out of one originally designed for land use is doomed. Look, for instance, at the F-111B compared to the F-14A. Or one can read about the struggles of the Seafire.

The P51 was not designed as a carrier aircraft. More specifically:
The airframe was not designed with a tail hook in mind. Putting a tail hook on a P51 airframe and then subjecting it to the stresses of a carrier landing would probably have pulled the tail off.
It doesn't have folding wings. Would have taken up a lot of room on a carrier deck and below deck, limiting spotting, and limiting the number of aircraft that could be launched within a given time frame. Being able to launch a large number of aircraft in a short period was a huge advantage, especially if an enemy raid is incoming.
The landing gear would not be rugged enough to handle carrier landings. To bring it up to that standard would necessitate both heavier gear and a heavier wing spar to take the stress.
The water cooled engine was not suitable for carrier operations. Heavier, and one lucky bullet meant the plane was going in the drink... and the pilot. The chances of rescuing a pilot whose location was unknown in the Pacific ocean were just about zero.
Aircraft design, even then, was a precise art, with tradeoffs to meet the desired goal. Changing the design later to meet a very different goal is likely to upset a lot of other design features. Simpler just to design a carrier aircraft from the ground up.
It is true that the Spitfire was redesigned for carrier operation as the Seafire, with decent results, but the British didn't have the resources to support a lot of different aircraft.
Note also that a dedicated carrier aircraft with performance in the general vicinity of the P51 was already available: the F4U Corsair.

The Corsair was a good plane but was used more for ground operations. If anything made the Mustang unnecessary for the Navy it was the F6F Hellcat which replaced the Wildcat as the Navy's mainstay for carrier operations. The Hellcats performance in the Pacific was incredible (4,947 of 6477 enemy planes shot down) and was praised by many pilots. By the time the evolution of the Mustangs would have been good enough for the Navy they already had the Hellcat which started being used in 1943.

Part of the reason that the Mustang was not used for aircraft carriers was that it was not needed. The US already had airbases in Iwo Jima and Okinawa were Mustangs could escort B-29s. And, at the end of the war, the US was more preoccupied in making jet aircraft for the future such as the FH phantom which was the first purely jet powered aircraft to land on an aircraft carrier or the F9F Panther.

From Michael O'Leary's "United States Naval Fighters of World War II", "Extensive testing had taken place between the Corsair and other types of Allied fighters...  The Corsair was tested against just about every fighter the Navy could get their hands on...it was concluded that the Corsair, which outweighed the Mustang by almost 3,000 lbs., was superior to the Mustang in all respects."

When citing a book, it would be good practise to mentio  page, if not for anything else, then for a feeling of credibility.


text:
What are these boxes built into the tails of some fighters?
In looking at European-designed fighters of the 4th and 4.5th generation, I keep seeing a common design feature; a box-like structure built into the tail, often in the top half or third. Some examples:
Saab Gripen

Mirage 2000 (this one's more complex and less box-like but the arrangement is very similar)

Rafale

Eurofighter Typhoon (this one looks markedly different, much lower and more like an intake)

Panavia Tornado (this one has two main protrusions from the tail, one much like the Typhoon's, the other more like the Gripens or Rafales)

SEPECAT Jaguar (you know what you're looking at by now)

What is this box? My best guess is some sort of avionics/sensor package, maybe RWR/missile warning. What's odd to me is that this box-in-tail arrangement is not seen on any relatively late-model U.S. or Soviet fighter; you'd think if the Europeans were onto something with this placement, the U.S. or Soviets would have tried it out at least once.
The F-15 has what I think is an RWR probe on top of the left tail, but the tail itself is pretty clean:

The F-16 does have a boxy construction flaring out at the top of the tail, but the front is clean:

The F/A-18 has some trailing-edge bulges but again very clean:

Su-27, ditto to the F-18 (it does have that big probe between the engines though):

MiG-29, same thing:

I could go on but you get the point, Soviet and U.S fighters seem to have passed on whatever this package is in the tail. So, what is it, why is the arrangement limited to European fighters (for the most part) and how do other regional designers accomplish whatever these do?

Very good question Keith I couldn't even find the answer on google. I am guessing it is a radar warning system. I beleive that the f-16, 15, and 18 may have a different missile warning system.  Thats probably why you don't see it on the other aircraft because they use a different system. Just a theory though.

Great question! Want to credit your pics?  ;)

I'm not sure it is a comparable device on all the aircrafts. The ones from the typhoon and the lower one on the tornado seems to differ by being equipped with an air intake

You're right. It's the ECM/EW antenna/equipment (fairing) in all the aircrafts except Typhoon.
This photo shows the details of EW/ECM suite in Gripen.

Source: www.w54.biz
In Typhoon, it is the engine bleed air heat exchanger. The part is in detail here.

Source: b-domke.de

On the tornado the box at the top of the fin is the RHWR basically to warn the A/C if there is a radar locking on to them. The lower protuberance like the typhoon is an intercooler intake.


text:
How does one develop artificial stabilization for aircraft uncontrollable without it?
In an answer about the F-117 Peter Kämpf writes

F-117 (...) is unstable and uncontrollable without artificial stabilization.

I wonder how such an aircraft comes to existence, specifically how one develops the program without which the aircraft can't be flown.
How one establishes (presumably in a wind tunnel using a scaled model) that the plane will not be stable or controllable, but it can be helped by an artificial stabilization system well enough to be flyable? How does one develop the system itself? How it is determined that the stabilization system has became mature and reliable enough to permit test flights?
Sorry about the question being somewhat blurred, I realize I don't even know what exactly to ask about. Any suggestions or reasonable edits welcome (in worst case I can roll the edit back).

This would probably take a college degree to understand. Short answer is, as long as things can be modeled mathematically, like being represented by differential equations, you can develop control rules for it, things like three wood sticks stacked vertically and balanced by a robotic hand. Modeling, controlling, simulation, and validation each has an entire science for it.

Except the "determine that.....mature and reliable" part. For instance take a look at how many test pilot have died during early testing of each fly-by-wire equipped airplane.

Most modern high agility ariplanes (such as fighter jets) are unstable in the sense that (among other things) their center of gravity (nearly) coinsides with their center of lift (i.e. they are wildly out of balance). The benefits include the ability of the airplane to react to control inputs nearly instantaneously. That the design will be unstable can be determined at a very early stage in the process (during the 'sketch' phase, really). Given a fast enough control system, nearly anything can be controlled (and modeled) so to answer your second question, to design a control system, all one needs to know is how complicated the system is (the order of the system) and how fast it should be. The first question can be answered based on very general principles (most aircraft can be modeled by a fourth order system). The second question is also easy to estimate (100 Hz is usually enough, don't ask me how I know this).
Of course, tricky regimes (supersonic, transonic, supercritical angle of attack, etc.) might require some time in the tunnel but these are to determine some parameters of the general model that has been decided on at the design stage.
That the system works is usually not in question before the plane is tested. Whether a human pilot will find it controllable is another matter. This is why the design of a modern high agility aircraft is done in parallel with a simulator design to see how the pilot would react. The simulator of course, is based on the same model that the actual design is (and is constantly modified as more experimental data becomes known).
Finally, even if the airplane is well designed, and everything works, the certification stage is where most accidents happen. For example, to test the single engine performance of a twin engine airplane the tests must be carried out at near sea level pressure, quite low to the ground. Not much time to react when the plane gets too slow.
A good book to read about these issues is Aircraft design: a conceptual approach by D. Raymer. You will quickly discover that one can practically calculate the look of the plane (controls location, high-wing, low-wing, where the engines go, etc.) based on its mission.

I'd give you another upvode if I could for the book reference alone!

There seems to be some kind of stubborn myth that unstable systems are impossible to control by humans, and you need some high tech computer magic to do it. This is not true.
I invite you to take a broomstick, tennis racket or baseball bat, and balance it on one end. If you succeeded: congratulations! You just stabilized an unstable system! Now continue doing this while reading an after-takeoff checklist. You will likely drop the broomstick in the process. Alternatively, try and balance a pencil instead of a broomstick. You will find this much more difficult or indeed impossible.
There are two things to take away from this. Unstable systems are simply any system that 'falls over' when you do nothing to correct for it, and secondly, unstable systems can be stabilized using a feedback controller. This controller (whether it is you or a computer) looks at the error (difference between the actual position and the desired position), and calculates a suitable actuator output.
The above example however demonstrates that humans do not make great feedback controllers. They can't multitask well, which is detrimental for unstable systems: when you let go of the controls for just a second, any disturbance will exacerbate itself; and secondly, for systems with a very short time constant (like a small pencil), the reaction time (in control terms: phase lag) of humans is too large to stabilize the system.
This is where the computer comes in. Based on a model of the aircraft dynamics, a controller is designed which stabilizes the system (and while this is perhaps not very easy, it is perfectly possible to design a controller 'offline', i.e., without the actual aircraft, only with a mathematical model). Depending on the model accuracy and the control design, this stabilizing controller may have some limitations. In control engineering, you can generally choose between either a quick reaction time to a (pilot) input, or a very stable system, but there is always a bit of a trade-off in 'agility' versus 'twitchiness'.  See @alexh's answer for how they solve this: they put pilots in a simulator (sometimes, this is an actual aircraft modified to behave like the target aircraft), and determine the best controller. A key point here is that the pilot is also part of the whole control loop; minor deficiencies in the computer controller can be corrected by the test pilot.
Secondly, there is a concept called 'region of attraction': for unstable systems, your controller may only work in normal conditions. If your broomstick were upside-down (hanging from your hand), it's a non-trivial task to upright it again. Similarly, if your aircraft is in a flat spin, you may need to revert to another controller to regain control. Note that pilots also revert to this kind of feed-forward control in a spin: kick down the rudder, and don't let go until you're out of the spin again. For unstable aircraft, there may not always be a way to regain control (for example, if the aircraft is very stable flying in reverse), which is why bailing out is an important ability for test pilots in unstable aircraft.
Finally, there is the point of mechanical linkage. In a simple aircraft, the controls are directly linked to the control surfaces. In an unstable aircraft, this is undesirable as the pilot may cause pilot induced oscillations (which they are prone to do even in stable aircraft!). Instead, the pilot's input are fed into the flight computer, which makes the aircraft feel stable as far as the pilot is concerned. This means that these aircraft cannot be flown without a computer, not necessarily because it is difficult, but simply because the pilot does not directly control the aircraft. Test flights are still possible if the computer is programmed with a marginally stable controller (whether they are successful, history will tell...)

Agree w.r.t. control of unstable systems is possible by humans, after all the original Wright flyer is an unstable design. It is only the high levels of instability on modern aircraft has been made possible with the introduction of flight control systems. The time to double amplitude of the system such that a pilot would be unable to control it. However a modern FCS will mix a blend of a quick system and a stable system. You need a quick system to avoid PIO but you can wash this out and feed in the stable system for a trimmed condition.

also just to point out it is possible to have a mathematical model of the pilot as well so the system modelling does include pilot in the loop analysis.

The entire system is mathematically modelled and tested prior to first flight.
You use empirical methods (ESDU), wind tunnel data and CFD to build an aerodynamic model that includes variations in Mach No., Alpha, Sideslip and control surfaces. You build models of the airdata system, engines, hydraulics, actuators and FCS. You include sensor models, analogue to digitial interfaces. Also have a set of equations of motion and an atmospheric model.
You then combine all the models together and analyse them as a complete system. Check the linear stability, gain and phase margins etc. Build a flight simulator to assess the handling qualities. The modelling allows you to test the system robustness by throwing lots of extreme tolerances at the system and making sure it's still safe.
You can then perform rig testing so for example replace the actuator model with real hardware and check the real hardware performs as predicted by the model.
Once you have tested everything and you have evidence of your work to convince the authorities that your design is safe you can go and fly.
It's not finished yet because you record all your flight data and match the data to your models, correcting and fine tuning the models when you see any discrepancies.
The best part is when you are involved in a first flight and the first comment from the test pilot when he landed was "that flies just like the simulator", it gives you confidence that your modelling is pretty good.